[H-GEN] Mail problems.......

Anthony Towns aj at humbug.org.au
Mon Sep 22 16:37:47 EDT 1997


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On Sun, 21 Sep 1997, Michael Anthon wrote:

> > [...] your problem is probably related more to how your
> > ISP connection is set up than masq or whatever. I'd check:
> > 	a) that you can move large files about in reasonable time.
> > 	   Try ftp. I've little idea how to fix this. Check that your
> > 	   modem is set up right, that your pppd MTU and MRU are
> > 	   reasonable, stuff like that. 
> Yep, OUTGOING ftp is also slow

Okay. I assume your ping response times to your mailserver are okay. 
(~400ms, hopefully)

> LAN connections between the two boxes seem to work perfectly.  Following is 
> the output from ifconfig.  This shows a fairly significant number of errors 
> on the incoming PPP, I wonder if this is a cause/symptom of my problem 
>
> ppp0      Link encap:Point-Point Protocol
>           inet addr:203.20.132.66  P-t-P:203.20.132.2  Mask:255.255.255.0
>           UP POINTOPOINT RUNNING  MTU:1500  Metric:1
>           RX packets:7401 errors:702 dropped:702 overruns:0
>           TX packets:8453 errors:0 dropped:0 overruns:0

FWIW: you can possibly use pppstats(8) to check your throughput (both
ways) in real time. If you've got it installed, anyway.

Some things to check:

	- Are you sure your modem initialisation string is right?

	- Are you using a "sensible" computer<->modem bps rate?
		(setserial?)

(could someone who knows about these give an explanation of what
constitutes "sensible" for both of these, btw?)

	- Can your ISP really cope with such a large MTU? Robert's
	  scripts uses a (somewhat low) value of 296, the default is
	  (I think) 1005, and that's also want Prentice (UQ)
	  recommends (I think). I'd try dropping it to ~500, at least.
	  (move it gradually back up once you get it working)

	- What is your MRU set to? Changing this _may_ affect the
	  error rate (my guess would be the smaller, the less that
	  errors will affect your throughput). 1500 has worked for me
	  quite pleasantly, although again Robert's script uses 296.
	  (also, the smaller, the more that packets have to be split
	  and then put back together later, so given an error-free
	  link, bigger should be faster, up to a point)

Another hint is to add the argument "debug" to the pppd line, and look
at what appears in /var/log/debug for anything useful. This might give
you a clue as to when the RX errors are happening. 

> Try http://www.qmail.org/

Thanks.

Cheers,
aj

- --
Anthony Towns <aj at humbug.org.au> <http://student.uq.edu.au/~s343676/>
I don't speak for anyone save myself. PGP encrypted mail preferred.

``Like the ski resort of girls looking for husbands and husbands looking
  for girls, the situation is not as symmetrical as it might seem.''

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